So I guess there wasn't a way to construct the bridge in situ so they built it a mile upriver and floated it into place.

News article, with video.

I did some work for a guy who was in this line of work. His company actually pioneered the process of building off site and then bringing it in before he was even born.

He said the long and short of it was that it actually saved time and money. They can build it where it has favorable access to equipment and supplies, and reduces the disruption to traffic on site. They got started with the railroads, because they could replace an entire bridge in a day or two.

I drive by this twice a day and watched them set the bridge. They certainly made it look easy.

I want one of those on my property. With a private clubhouse at the co-vertex. Yeah, and with birchbeer on tap!

It has long been thought that when the time comes to build a "beanstalk" AKA a "skyhook" or "space elevator" it will be built in space and flown in to place. I have read several Sci-Fi depictions of a scenario where this is done, apparently the physics are not that hard to work out, and the price tag of building it is estimated to be somewhat less than what we've spent on the space program so far. Sort of the ultimate bridge construction project.

The bridge that collapsed near FIU in Miami a couple years ago was built adjacent to the site and then moved into place, as well. I don't think it was determined that the construction method led to its demise but I haven't kept up with it.

quote:

Originally posted by architect:
It has long been thought that when the time comes to build a "beanstalk" AKA a "skyhook" or "space elevator" it will be built in space and flown in to place. I have read several Sci-Fi depictions of a scenario where this is done, apparently the physics are not that hard to work out, and the price tag of building it is estimated to be somewhat less than what we've spent on the space program so far. Sort of the ultimate bridge construction project.

I see several problems with a "space elevator":
1. How do you keep things from crashing into it?
2. Wouldn't every part of the device be trying to orbit at a different velocity? Wouldn't that teaar it apart?
3, Assuming it is built and works, where are you when you get to the top? Some station in geocentric orbit.
4. How long does a trip up or down take? 22,700 miles is a long distance.

Just idle thoughts.

flashguy

All of these points have long been thought out:

1) you dodge them (by making the ground station mobile, e.g. at sea).

2) Not if the construction material is strong enough. So far, only carbon nanotubes and graphene are suitable candidates, But manufacturing techniques do not yet exist.

3) The actual "top" will be far outside the geosynchronous altitude, in the form of a huge counterweight to maintain tension on the cable. Launching payloads into orbit is simply letting them loose from the cable, no additional delta-vee need unless you want a different orbit. Far enough out, the payload is already doing more than escape velocity so you have "free" space travel.

4) Yes, but who would have thought that the world could be explored in less than 100 years by sailing ships doing less than 15 knots, so speed isn't in and of itself a huge factor. Main thing is the cost of using a space elevator is estimated to be 100x less than rocketry.

The International Space Elevator Consortium has considered all these and many more potential issues. They address some of them in their overview page. Admittedly, they are not an impartial party, but their estimate is that the first working space elevator will be built in the 2030's.

You lost me at “physics are not that hard to work out”. This concerning a subject where even the construction materials don’t even exist yet (saying carbon nanotubules and them actually working aren’t even in the same orbit). Plus, pretending like the price tag is known is pure Popular Mechanics cover art. Which I suspect is your source material.

Those TV shows that are about the Offshore Oil Rigs they build offsite and nove into place are similarly fascinating.

quote:

Originally posted by YellowJacket:
The bridge that collapsed near FIU in Miami a couple years ago was built adjacent to the site and then moved into place, as well. I don't think it was determined that the construction method led to its demise but I haven't kept up with it.

I remember that one. They insisted in having an all female engineering team. That worked out great!

quote:

Originally posted by .38supersig:

quote:

Originally posted by YellowJacket:
The bridge that collapsed near FIU in Miami a couple years ago ...

I remember that one. They insisted in having an all female engineering team. That worked out great!

Huh?

---

the probable cause of the Florida International University (FIU) pedestrian bridge collapse was the load and capacity calculation errors made by FIGG Bridge Engineers, Inc., (FIGG) in its design of the main span truss member 11/12 nodal region and connection to the bridge deck. Contributing to the collapse was the inadequate peer review performed by Louis Berger, which failed to detect the calculation errors in the bridge design. Further contributing to the collapse was the failure of the FIGG engineer of record (EOR) to identify the significance of the structural cracking observed in this node before the collapse and to obtain an independent peer review of the remedial plan to address the cracking. Contributing to the severity of the collapse outcome was the failure of MCM; FIGG; Bolton, Perez and Associates Consulting Engineers; FIU; and the Florida Department of Transportation (FDOT) to cease bridge work when the structure cracking reached unacceptable levels and to take appropriate action to close SW 8th Street as necessary to protect public safety. - wiki

quote:

Originally posted by YellowJacket:
The bridge that collapsed near FIU in Miami a couple years ago was built adjacent to the site and then moved into place, as well. I don't think it was determined that the construction method led to its demise but I haven't kept up with it.

The engineering was fine. The architects wanted it to look prettier so they moved some things around but never made sure that was okay with the engineers. The result was a bridge that couldn’t hold its own weight. The decision to install it without stopping traffic on US-1 below was idiotic.

Nothing wrong with the method.

quote:

Originally posted by 46and2:
Those TV shows that are about the Offshore Oil Rigs they build offsite and nove into place are similarly fascinating.

We actually build rigs and platforms in shipyards since it is so similar to building a ship, they have the heavy lift capabilities (e.g. cranes and/or SPMTs), and dry docks.

quote:

Originally posted by tatortodd:

quote:

Originally posted by 46and2:
Those TV shows that are about the Offshore Oil Rigs they build offsite and nove into place are similarly fascinating.

We actually build rigs and platforms in shipyards since it is so similar to building a ship, they have the heavy lift capabilities (e.g. cranes and/or SPMTs), and dry docks.

That's cool, and makes sense.